Expanding industry and an increasing number of applications have caused growth in the number of towers of great height (for example, a height of 75 feet or more). Typical applications include towers for power transmission, telecommunications, and industrial use. However, the capacity to build new towers is hampered by current construction methods, which are costly and time-consuming, and which rely on the availability of specialty equipment.
Current methods require constructing the tower in sections to achieve a vertical position. Typically, a large crane is brought to the construction site, where the crane is used to lift segments of the tower, one-by-one, into place on top of each other. Because of the height of the towers, typically varying between 120 and 400 feet, the present systems cannot raise and stabilize the tower without doing it in sections. Each section must be lifted to a height with a crane, using taller and taller cranes, and then secured into place at that height. This process usually requires long periods of time to complete. Furthermore, constructing towers using current techniques often requires taking advantage of small windows of time where the wind is sufficiently still to raise, place and attach consecutive sections.
These disadvantages, while ubiquitous to tower construction in general, are compounded by the requirements of certain tower applications. One such application is wind turbine towers. The need for wind turbine towers has increased as harnessing wind energy has gained acceptance as a viable means of generating electrical power for industrial and consumer uses. Large scale capture and conversion of wind energy requires the placement of wind turbines at a suitable elevation above the ground to capture the wind flow free from the interference and turbulence caused by the surface of the surrounding terrain. To achieve placement at such height, towers of great size are used to support the wind turbines. Due to the relatively small electrical generation capacity of each individual wind turbine, numerous towers are required.
By their nature, optimal wind turbine tower sites are usually subject to high winds, which exacerbates the problem of completing construction during the “low-wind” time window. Further, moving a crane onto the typical wind turbine construction site can be quite difficult since many wind turbine construction sites are in remote locations far from improved roads. Existing roads to the site may not have sufficient bearing strength to support the transit weight of the large crane required by current methods. Thus, roads to the construction site are built or improved to allow the construction cranes to be brought on site. In some cases, these roads must also be removed after construction due to limitations on land leases and rights-of-way. The required construction (and subsequent removal) of these roads creates a large collateral cost to the wind turbine tower construction.